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This is the 28th volume of Memorial Tributes compiled by the National Academy of Engineering as a personal remembrance of the lives and outstanding achievements of its members and international members. These volumes are intended to stand as an enduring record of the many contributions of engineers and engineering to the benefit of humankind. In most cases, the authors of the tributes are contemporaries or colleagues who had personal knowledge of the interests and the engineering accomplishments of the deceased. Through its members and international members, the Academy...
This is the 28th volume of Memorial Tributes compiled by the National Academy of Engineering as a personal remembrance of the lives and outstanding achievements of its members and international members. These volumes are intended to stand as an enduring record of the many contributions of engineers and engineering to the benefit of humankind. In most cases, the authors of the tributes are contemporaries or colleagues who had personal knowledge of the interests and the engineering accomplishments of the deceased. Through its members and international members, the Academy carries out the responsibilities for which it was established in 1964.
Under the charter of the National Academy of Sciences, the National Academy of Engineering was formed as a parallel organization of outstanding engineers. Members are elected on the basis of significant contributions to engineering theory and practice and to the literature of engineering or on the basis of demonstrated unusual accomplishments in the pioneering of new and developing fields of technology. The National Academies share a responsibility to advise the federal government on matters of science and technology. The expertise and credibility that the National Academy of Engineering brings to that task stem directly from the abilities, interests, and achievements of our members and international members, our colleagues and friends, whose special gifts we remember in this book.
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BY KHALID AZIZ AND GEORGE HIRASAKI
HENRY HERBERT RACHFORD JR. was born June 14, 1925, in El Dorado, Arkansas, to Henry H. Rachford Sr. and Helene Akin Rachford. After his family moved to Houston when he was a young boy, Henry graduated from Lamar High School in 1942. He earned his B.S. in chemical engineering (1945) and M.A. in chemistry (1947) from Rice University, followed by his Sc.D. in chemical engineering from the Massachusetts Institute of Technology (1950). In 1949, he joined the Humble Oil and Refining Company (now ExxonMobil). He died on Oct. 31, 2022, at age 97.
Recognizing early in his professional life the potential of digital computers to solve critical industrial problems, Henry began developing computational tools to achieve this goal. In 1952, he coauthored a technical note with J.D. Rice, published in the Petroleum Transactions of the AIME (American Institute of Mining, Metallurgical, and Petroleum Engineers), presenting a procedure for computing vapor/liquid equilibria of hydrocarbons systems using digital computers. This ingenious Rachford-Rice procedure remains widely used today in applications such as hydrocarbon refinery design, multiphase pipeline systems for hydrocarbon transport, and modeling hydrocarbon recovery processes.
When Rachford joined Humble, his research focused on using computers to simulate petroleum reservoir behavior during recovery operations. The techniques he and his colleagues developed are equally applicable to solving many other problems described by partial differential equations. His primary emphasis was on problems involving simultaneous nonlinear partial differential equations in three dimensions where no analytical solutions were possible. In 1953, he co-authored a paper1 on one-dimensional gas flow in porous media, described by a nonlinear partial differential equation. This was followed by a series of papers2 addressing increasingly complex problems. He and his colleagues developed useful numerical techniques — along with the analysis of stability, convergence, and roundoff errors of these techniques.
In the early 1950s, Rachford pioneered techniques for solving complex multiphase, multicomponent flow problems in porous media. The computers available at that time were severely limited in terms of speed and memory, requiring coding in machine language, and developing techniques able to reduce multidimensional problems into a series of simpler one-dimensional problems. This work led to the invention of the Alternating-Direction Implicit (ADI) method, described in a 1955 Society for Industrial and Applied Mathematics (SIAM) paper coauthored with D.W. Peaceman.3 ADI helped drive industry-wide acceptance of computational petroleum reservoir models — among the earliest examples of digital twins now widely used in various fields. The operator splitting concept introduced in the SIAM paper has since been used in many other areas, including weather prediction. One of Rachford’s students, Richard Kendall, later joined Humble in 1973 and led the development of petroleum reservoir simulation technology. In 1964, Rachford joined the Rice University faculty as a professor in the Department of Mathematical Sciences — the precursor to the Department of Computational and Applied Mathematics, established in 1970. His research and educational contributions while at Rice are impressive. During his 18 years there, he continued advancing the development and analysis of numerical techniques for solving partial differential equations. According to the Mathematics Genealogy Project, he mentored nine Ph.D. students and has 175 mathematical descendants, including Mary F. Wheeler (NAE 1998) at the University of Texas and Todd Dupont at the University of Chicago. Dr. Rachford retired from Rice University in 1982.
In 1969, he co-founded Dupont Rachford Engineering Mathematics Company, which was later acquired by a series of other companies. Rachford continued working with each successor. His most important contribution during this period was leading the development of a comprehensive tool for modeling fluid flow in pipeline networks. The resulting software, now maintained by DNV (a corporation owned by the Det Norske Veritas Foundation), is widely used for pipeline design, operations optimization, operator training, estimating the conditions of operating pipelines, and leak detection. A key aspect of this work was integrating modeling with data acquisition systems. In a 2000 paper, presented at the Pipeline Simulation Interest Group Annual Meeting, Rachford and Carter demonstrated how pipelines with time-dependent delivery volumes at various load points could be controlled by dynamically adjusting compressor station pressure setpoints to optimize flow and line pack within a predetermined time interval. These setpoint values are computed to achieve the optimum target state in a predetermined time interval.
In 2000, Rachford was elected to the National Academy of Engineering for his “contributions in the numerical solution of partial differential equations to solve petroleum reservoir and pipeline hydraulics problems.”
He was predeceased by his parents, his first wife, Jo, and his second wife, Sylvia. He is survived by his daughters, Susan Rachford Imre (husband Tom) and Laurie Rachford; three grandchildren, Stephanie Fallon (husband Aaron), Chris Lohmann, and Alex Imre; and his great-granddaughter, Poesy Fallon.
Acknowledgments: This tribute was made possible with contributions from Mary Wheeler, Todd Dupont, and Richard Kendal. Laurie Rachford, Henry’s daughter, reviewed and approved the tribute.
________________________________ 1Bruce CH, Peaceman DW, Rachford HH, Rice JD. 1953. Calculations of unsteady-state gas flow through porous media. Trans. AIME 198:79. 2Rachford HH, Taylor RD, Douglas J, Dyke PM. 1958. Application of numerical methods to predict recovery from thin oil columns. Trans. 213:193-201; Douglas J, Peaceman DW, Rachford HH. 1959. A method for calculating multi-dimensional immiscible displacement. Trans. 216:297-308; Peaceman DW, Rachford HH. 1962. Numerical calculation of multidimensional miscible displacement. SPE J. 2:327-39; Rachford HH. 1964. Instability in water flooding oil from water -wet porous media containing connate water. SPE J. 4:133-48. 3Peaceman, DW, Rachford Jr HH 1955. The numerical solution of parabolic and elliptic differential equations. Journal of the Society for industrial and Applied Mathematics 3(1):28-41.